Australia has accepted a request from Malaysia to take charge of the "southern vector" of the search for a Malaysia Airlines jetliner missing for more than a week with 239 people on board, Prime Minister Tony Abbott said on Monday.

Abbott said he had offered additional surveillance resources to bolster the two Australian Orion aircraft already searching for the plane during a recent phone call with Prime Minister Najib Razak.

"He asked that Australia take responsibility for the search in the southern vector, which the Malaysian authorities now think was one possible flight path for this ill-fated aircraft," Abbott told lawmakers in parliament.

"I agreed that we would do so."

The search for flight MH370 is focusing on a wide strip of territory either side of two arcs formed by satellite plots of the aircraft's last known possible position.

The southern Indian Ocean is one of the most remote places in the world and also one of the deepest, posing potentially enormous challenges for the international search effort.

The northern vector of the search stretches through Thailand and China and bends towards India, Pakistan and then Central Asia, over some of the world's most strongly guarded defenses.

Abbott said Australian Defence Force chief David Hurley was in discussion with his Malaysian counterparts about how best to deploy the additional resources, without providing further details, in the search for the Boeing 777-200ER.

On Sunday, Australia shifted one of its two Orion aircraft searching for the missing plane further south in the Indian Ocean, at Malaysia's request. The aircraft is now searching the ocean to the north and west of the remote Cocos Islands. The second Orion is continuing to search west of Malaysia.